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 Copyright (c) 2008, 2009, Memo Akten, www.memo.tv
 *** The Mega Super Awesome Visuals Company ***
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#pragma once

#include "ofMain.h"
#include "ofxMSAConstraint.h"


class ofxMSACollision : public ofxMSAConstraint {
public:
	friend class ofxMSAPhysics;
	
	bool	bCollided;		// whether collision happened or not (upto app to clear the flag after reading it)

	ofxMSACollision(ofxMSAParticle *a, ofxMSAParticle *b) {
		this->_a = a;
		this->_b = b;
		_type = OFX_MSA_CONSTRAINT_TYPE_COLLISION;
		setClassName(string("ofxMSACollision"));
		bCollided = false;
	}


protected:
	void solve() {
		// problems with binning!
//		if(_params->doWorldEdges && !_a->isInSameBinAs(_b)) return; // if world edges have been set, check to see if particles are in same bin

		float restLength = _b->getRadius() + _a->getRadius();
		ofPoint delta = (*_b) - (*_a);
		float deltaLength2 = msaLengthSquared(delta);
		if(deltaLength2 >restLength * restLength) return;
		
		bCollided = true;
		float deltaLength = sqrt(deltaLength2);	// TODO: fast approximation of square root (1st order Taylor-expansion at a neighborhood of the rest length r (one Newton-Raphson iteration with initial guess r))
		float force = (deltaLength - restLength) / (deltaLength * (_a->getInvMass() + _b->getInvMass()));

		if (!_a->isFixed()) *_a += delta * (_a->getInvMass() * force);
		if (!_b->isFixed()) *_b -= delta * (_b->getInvMass() * force);
	}

	void debugDraw() {
        ofSetColor(255, 0, 0);
        ofxMSAConstraint::debugDraw();
	}

};
